The matrix protein of bones play key roles in the structure and function of these tissues. Our objective in this investigation is to study the biosynthesis of these macromolecules and to understand the regulation of their expression. The expression of bone matrix proteins have been studied by constructing recombinant cDNA libraries from bone cell mRNA. cDNA clones encoding several bone and tooth matrix proteins have been isolated using expression DNA vectors and polyclonal antisera directed against individual bone matrix and ameloblast proteins. The clones were used to study the primary structure and regulation of expression of these genes in cultured bone cells.